A biosensor is used to detect or quantify a target substance contained in a sample. A high affinity between streptavidin and biotin may be used in the biosensor. Specifically, streptavidin is immobilized on the biosensor. The target substance is modified with a biotin molecule. When the target substance is supplied to the biosensor, the target substance is immobilized on the biosensor due to the high affinity between streptavidin and biotin.
Patent Document 1 discloses a prior biosensor utilizing the high affinity between streptavidin and biotin. FIG. 2 shows a biosensor disclosed in FIG. 7 of the Patent Document 1.
According to the description regarding FIG. 7 of the Patent Document 1, the biosensor is used for screening of biomoleculer activity. The biosensor comprises a monolayer 7, an affinity tag 8, an adaptor molecule 9, and a protein 10. The monolayer 7 is composed of a self-assembled monolayer represented by chemical formula: X—R—Y (see Page 24 lines 23-26, Page 25 lines 3-20, Page 25 line 27-Page 26 line 13, and Page 26 lines 14-22 of Patent Document 1). Examples of X, R, and Y are HS—, an alkane, and a carboxyl group, respectively (see Page 25 lines 3-20, Page 25 line 27-Page 26 line 13, and Page 28 lines 21-23 of Patent Document 1).
The affinity tag 8 and the adaptor molecule 9 may be composed of streptavidin and a biotin molecule, respectively (see Page 36 lines 3-5 of Patent Document 1).